Adolescent use of tobacco, alcohol, and illegal drugs has increased recently, after nearly two decades of decline. One effective method of renewing prevention efforts is cross curriculum exposure to substance abuse issues via CAI and interactive video. Instruction in the scientific method using drug examples can provide a powerful medium for this exposure. Despite the critical importance of teaching students logical thinking and the scientific method, students receive little instruction on either. Performance of American students, both in scientific reasoning and scientific principles, is very low by international standards. Research supports teaching scientific method, and the underlying logic and critical thinking skills, by using explicit rules in small incremental steps. Within the instruction on scientific method and decision-making a powerful substance abuse prevention message can be delivered. In Phase I, four lessons in logic, critical thinking, scientific method will be developed and evaluated. The Phase I prototype will include computer presentations and printed student materials. The prototype efficacy will be evaluated with 40 middle school students. In Phase II, two complete 50 lesson CD ROM-based programs will be developed--and then tested for effectiveness in a randomized control trial. PROPOSED COMMERCIAL APPLICATION: This project will lead to the Phase II production of two 50 lesson CD-ROM-based instructional programs that teach decision-making skills and their application to substance abuse issues. One program each will be designed for middle school students and high school students. Both programs will incorporate live video, animation, and still frame problems. The products will be attractive to middle schools and high schools for use in virtually any science class as well as to the home use market.